A tipster told the British website that pictures of well-endowed black men are "automatically appearing" when they peruse the hashtag on Twitter. The "problem," as PC Pro labels it, is caused by Twitter's photo preview feature, which links to hardcore imagery without filtering it.

"Such a search throws up graphic images with no warning of adult content, alongside trailers for Radio 1 shows and BBC nature programmes," laments the site.

Indeed, a Twitter search for #BBC reveals a few johnsons scattered in between Sherlock posts and a Radio 1 playlist account. Most are posted by "XXX" usernames—which is usually a big warning that there's porn around.

Twitter told the website it only screens for forbidden material (like pornography) on profile pictures and backgrounds and that tweets are "not mediated." The company encourages users to flag inappropriate content, but doesn't immediately remove it.